Drainage Layer?

[Bretts]

Here are the two articles Mojo
http://bonsaiwonders-art.blogspot.com/2 ... ayers.html
This second one is very interesting but the one main point of interest here that the quote comes from is under
Media drainage
http://www.ultragro.pl.net/mediasepc.htm
Maybe that will answer your first question!

Shallower containers that hold the same volune of media as deeper pots, have a larger surface area of soil. Surface tension in shallow pots is greater because there is a higher surface area. Drainage, or more accurately water percolation is therefore slowed more by surface tension than in a deeper pot.

Having said that, Shallower pots, with their comparively larger surface area per volume of soil when compared to deeper pots, are more succeptible to moisture loss through evaporation and have less insulation against temperature change.


By the way, what is this article that keeps getting refered to?

Cheers,
Mojo

Yes this I understood before reading the articles. Take two pots of equal volume but one is tall and the other is a flat shape ie flat oval compared to a cascade pot of the same overall volume.
The flat pot will hold more water by surface tension.
But these articles go a step further and state that a pot that is taller although the same diameter as a shorter one and hence more volume will actually retain less water than the shorter one with less volume.
Kinda hard to comprehend and it was this conclusion in the first article that had me thinking he had come to a false conclusion. Yet this other article is suggesting the same thing.
I guess it can easily be tested with a couple of cut off plastic containers of different heights full of medium(with holes in bottom for drainage). If they are correct the water level of the shorter container will be seen to be higher
Edit:

by Mojo Moyogi » 17 minutes ago

Ok, I found the article. Reading it now. It may well be BS.

Mojo

[Bretts]

63pmp
10 cm of fine mix will have more water than 7cm of fine mix simply because it is deeper, but the water content at the bottom 7 cm’s is the same.

Sorry Paul I found your post very confusing but if I take this small quote as being two pots of equal diameter then the two articles suggest otherwise that the 7cm pot will retain more water than 10cm. But I think I agree with most of the rest of your statement. But I am sure you mixed some numbers up

[Bretts]

"The best environment is a soil that dries out daily. The best potting practice is to shift to the next larger size pot after each time the plant becomes root established as evidenced by forming an intact rootball. UC Davis studies have shown this, and I have conducted my own studies with Acer palmatum, which have verified it to my own satisfaction. It is not a marginal effect; the resulting growth improvement is significant. "
Brent Walston

I reckon that is on the money.

Agree heaps again Deemon. This technique is described in the growing pines from seedlings articles. Minimal root disturbance while potting up each year creates the perfect environment for fast root growth.
It is interesting to note that different grades of soil in the planting medium as we discuss here is also a major component in that growth plan. As the guy states in the first article what are they trying to accomplish.
I will have to get the authors name instead of saying the guy that wrote the article Thats a little slack

[63pmp]

Sorry Paul I found your post very confusing but if I take this small quote as being two pots of equal diameter then the two articles suggest otherwise that the 7cm pot will retain more water than 10cm. But I think I agree with most of the rest of your statement. But I am sure you mixed some numbers up

Diameter of pots is irrelevant, it is the vertical depth of a pot that is important think from the bottom up, not the top down, If you have 2 pots, one 15cm tall, the other 10 cm tall, water drain etc. The water retained in the 10 cm pot will be equal to the bottom 10 cm of soil in the 15 cm pot. If you only have a 5cm deep pot, the water retained will be exactly the same as the bottom 5cm of soil in the 10 and 15 cm pot. However wide the pot is, is irrelevant. So a pot with 5cm depth will have less air for plants to breath, but also less water because there is less volume of soil.

Paul

[Mojo Moyogi]

Ok, I read the articles twice and my eyes are burning and my head hurts. I need some processing time I think.

Mojo

[Handy Mick]

Sounds good to me Paul!

[Bretts]

Sorry Paul I found your post very confusing but if I take this small quote as being two pots of equal diameter then the two articles suggest otherwise that the 7cm pot will retain more water than 10cm. But I think I agree with most of the rest of your statement. But I am sure you mixed some numbers up

Diameter of pots is irrelevant, it is the vertical depth of a pot that is important think from the bottom up, not the top down, If you have 2 pots, one 15cm tall, the other 10 cm tall, water drain etc. The water retained in the 10 cm pot will be equal to the bottom 10 cm of soil in the 15 cm pot. If you only have a 5cm deep pot, the water retained will be exactly the same as the bottom 5cm of soil in the 10 and 15 cm pot. However wide the pot is, is irrelevant. So a pot with 5cm depth will have less air for plants to breath, but also less water because there is less volume of soil.

Paul

That does sound feasible. It is slightly different than they are saying but still close enough that you all could be right I was thinking there had to be a piont where a shorter pot just could not carry as much water as a taller pot. I am only relying on trying to understand what they are saying and it is as confusing as Galileo's proven theory that all objects fall at the same speed. It goes against the grain of normal thinking.

[Bretts]

So if we have that soughted maybe we can consider what Grant said

Pot Size.

Ok ;if the so called drainage layer actually allows the pot to hold more water then would it be possible/preferable to go to a smaller pot? The Japanese say a lot of our trees are over potted.

Grant

The first thing I think of is trees that like a deep pot. Hornbeam is one and I think crab apple is another. If we use Paul's explanation this means that a deeper pot will have slightly more water and more air. If we go to a shallower pot there will be slightly less water and less air.
I think that makes sense.
So if we use a drainage layer we end up with a medium that is in effect a shorter pot with less air and less water.
Starts to sound like the answer is no to Grants question and a drainage layer in this instance is counter productive.

Hey I think we are making progress

[63pmp]

So what happens when we add a drainage layer of large particles? The finer potting mix on top has small pores, water does not want to drain into the gravel layer. We add water on top of the pot with a drainage layer, it passes through the layers of potting mix. Once the weight of water equals surface tension of the finer potting mix, water will stop flowing, we will then have a perched water table on top of the gravel, (since the gravel has large pores, these will drain, the air to fill them comes from below, via the drain holes in the pot, not through the upper layer of finer potting mix). Effectively what we are doing is raising the bottom layer of soil (in the pot). So if we have a 5cm deep pot, with 2cm of gravel, we will have 3cm thick layer of potting mix, which will behave like the bottom 3cm of the potting mix without a gravel layer. Once again think from the bottom up. The 3cm layer of potting mix will be like the bottom 3cm layer of the potting mix in any pot.

I really need some good diagrams, its really hard to explain this stuff using only words.

So if we use a drainage layer we end up with a medium that is in effect a shorter pot with less air and less water.
Starts to sound like the answer is no to Grants question and a drainage layer in this instance is counter productive.

YES!!!!!!!

Roots will not be air pruned in the gravel layer due to high humidity and some water being retained , only when they grow out of the drainage holes will they be pruned.



Paul

[Bretts]

The last part of your post was what I wanted to hear. The first part is kinda back where we started.
I agree about the diagrams maybe we can do that but I think we are getting there now

[Bretts]

Roots will not be air pruned in the gravel layer due to high humidity and some water being retained , only when they grow out of the drainage holes will they be pruned.

Yes in general here I agree. Although if the coarse layer was large enough Na ok that is just silly Hmm maybe not

Ok so I think we can find a constant here. When you are trying to use the smallest pot possible a drainage or coarse layer is counter productive but it could be very useful when growing on allowing you to use a larger pot while minimising the water volume in the pot. This results in allowing lots of room for growth of roots as the tree and medium combination ages.
Using a coarse layer will allow the tree to grow on without repotting. As Jamie suggested as the roots fill the coarse layer water will again syphon down to the bottom where the roots are now abundant.
This makes allot of sense why it is used in the Pine seedling program